Combine the WM_CHAR with WM_KEY* for key event flow.

ui/base/ime/input_method_win.cc

Index: ui/base/ime/input_method_win.cc
diff --git a/ui/base/ime/input_method_win.cc b/ui/base/ime/input_method_win.cc
index df75bb2ff90f40f332ab08c1a00964ae334a753e..e828ae08562d6ed44e118c758438701dd272c262 100644
--- a/ui/base/ime/input_method_win.cc
+++ b/ui/base/ime/input_method_win.cc
@@ -6,8 +6,10 @@
 
 #include "base/auto_reset.h"
 #include "base/basictypes.h"
+#include "base/command_line.h"
 #include "ui/base/ime/text_input_client.h"
 #include "ui/base/ime/win/tsf_input_scope.h"
+#include "ui/base/ui_base_switches.h"
 #include "ui/events/event.h"
 #include "ui/events/event_constants.h"
 #include "ui/events/event_utils.h"
@@ -31,8 +33,7 @@ InputMethodWin::InputMethodWin(internal::InputMethodDelegate* delegate,
       accept_carriage_return_(false),
       enabled_(false),
       is_candidate_popup_open_(false),
-      composing_window_handle_(NULL),
-      suppress_next_char_(false) {
+      composing_window_handle_(NULL) {
   SetDelegate(delegate);
 }
 
@@ -104,14 +105,41 @@ void InputMethodWin::DispatchKeyEvent(ui::KeyEvent* event) {
   }
 
   const base::NativeEvent& native_key_event = event->native_event();
+  BOOL handled = FALSE;
   if (native_key_event.message == WM_CHAR) {
-    BOOL handled;
     OnChar(native_key_event.hwnd, native_key_event.message,
            native_key_event.wParam, native_key_event.lParam, &handled);
     if (handled)
       event->StopPropagation();
     return;
   }
+
+  std::vector<MSG> char_msgs;
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
+      switches::kEnableMergeKeyCharEvents)) {
+    // Combines the WM_KEY* and WM_CHAR messages in the event processing flow
+    // which is necessary to let Chrome IME extension to process the key event
+    // and perform corresponding IME actions.
+    // Chrome IME extension may wants to consume certain key events based on
+    // the character information of WM_CHAR messages. Holding WM_KEY* messages
+    // until WM_CHAR is processed by the IME extension is not feasible because
+    // there is no way to know wether there will or not be a WM_CHAR following
+    // the WM_KEY*.
+    // Chrome never handles dead chars so it is safe to remove/ignore
+    // WM_*DEADCHAR messages.
+    MSG msg;
+    while (::PeekMessage(&msg, native_key_event.hwnd, WM_CHAR, WM_DEADCHAR,
+                         PM_REMOVE)) {
+      if (msg.message == WM_CHAR)
+        char_msgs.push_back(msg);
+    }
+    while (::PeekMessage(&msg, native_key_event.hwnd, WM_SYSCHAR,
+                         WM_SYSDEADCHAR, PM_REMOVE)) {
+      if (msg.message == WM_SYSCHAR)
+        char_msgs.push_back(msg);
+    }
+  }
+
   // Handles ctrl-shift key to change text direction and layout alignment.
   if (ui::IMM32Manager::IsRTLKeyboardLayoutInstalled() &&
       !IsTextInputTypeNone()) {
@@ -135,9 +163,20 @@ void InputMethodWin::DispatchKeyEvent(ui::KeyEvent* event) {
     }
   }
 
+  // If only 1 WM_CHAR per the key event, set it as the character of it.
+  if (char_msgs.size() == 1)
+    event->set_character(static_cast<base::char16>(char_msgs[0].wParam));
+
   ui::EventDispatchDetails details = DispatchKeyEventPostIME(event);
-  if (!details.dispatcher_destroyed)
-    suppress_next_char_ = event->stopped_propagation();
+  if (details.dispatcher_destroyed || details.target_destroyed ||
+      event->stopped_propagation()) {
+    return;
+  }
+
+  for (size_t i = 0; i < char_msgs.size(); ++i) {
+    MSG msg = char_msgs[i];
+    OnChar(msg.hwnd, msg.message, msg.wParam, msg.lParam, &handled);
+  }
 }
 
 void InputMethodWin::OnTextInputTypeChanged(const TextInputClient* client) {
@@ -219,11 +258,6 @@ LRESULT InputMethodWin::OnChar(HWND window_handle,
                                BOOL* handled) {
   *handled = TRUE;
 
-  if (suppress_next_char_) {
-    suppress_next_char_ = false;
-    return 0;
-  }
-
   // We need to send character events to the focused text input client event if
   // its text input type is ui::TEXT_INPUT_TYPE_NONE.
   if (GetTextInputClient()) {
@@ -554,10 +588,6 @@ bool InputMethodWin::IsWindowFocused(const TextInputClient* client) const {
 
 void InputMethodWin::DispatchFabricatedKeyEvent(ui::KeyEvent* event) {
   if (event->is_char()) {
-    if (suppress_next_char_) {
-      suppress_next_char_ = false;
-      return;
-    }
     if (GetTextInputClient()) {
       GetTextInputClient()->InsertChar(
           static_cast<base::char16>(event->key_code()),